Elevated levels of TNFa can produce fevers, malaise and weight loss in patients with mycobacterial infections or HIV. Thalidomide selectively reduces the serum levels of TNFa in these patients and may alleviate their symptoms. The metabolic effects of thalidomide that would arrest weight loss and allow patient to return to normal weight have not yet been elucidated. We admitted patients to the GCRC and established them on a metabolic diet. Patients were then treated with thalidomide. A longitudinal evaluation of metabolic function was undertaken to examine the impact of thalidomide. These studies are preliminary and require more patients for statistical validity. We plan to continue to refine our evaluations to understand more about the effects of both thalidomide and TNFa.